1. Field of the Disclosure
This disclosure generally relates to exploration and production of hydrocarbons involving investigations of regions of an earth formation penetrated by a borehole.
2. Description of the Related Art
Electrical earth borehole logging is well known to persons having an ordinary level of skill in the art, and various devices and various techniques have been described for this purpose. Broadly speaking, there are two categories of electrical logging apparatuses. In the first category, one or more measurement electrodes—current source(s) or sink(s)—are used in conjunction with a return electrode (which may be a diffuse electrode such as a logging tool's body or mandrel). A measurement current flows in a circuit that connects a current source to the measurement electrode(s), through the earth formation to the return electrode, and back to the current source in the tool. In a second category, that of inductive measuring tools, an antenna within the measuring instrument induces a current flow within the earth formation. The magnitude of the induced current is detected using either the same antenna or a separate receiver antenna. The present disclosure may be applied to both categories.
Spectral induced polarization (SIP) is a geophysical measurement method for determining the complex electrical impedance of an earth formation. SIP typically involves injecting an electrical current into the earth formation using one or more electrodes and measuring the voltage between one or more additional electrodes.